CA1314985C

CA1314985C - Optical head

Info

Publication number: CA1314985C
Application number: CA000572803A
Authority: CA
Inventors: Nobuyoshi Andou; Hitoshi Imai
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1987-07-24
Filing date: 1988-07-22
Publication date: 1993-03-23
Anticipated expiration: 2010-03-23
Also published as: JPS6418423U; DE3870531D1; EP0300820B1; US4861139A; JP2518213Y2; EP0300820A2; EP0300820A3

Abstract

ABSTRACT OF THE DISCLOSURE

The present invention relates to an optical head of an optical recording and reproducing device for optically re-cording or reproducing informations. In the optical head according to the present invention, when a holder, which is provided with an optical element fixedly disposed thereon, is fixed to a housing member, the holder is housed in a guide hole of the housing member and then a screw is screwed into a tapped hole formed in the housing member not so as to reach the guide hole to press a bottom portion of the tapped hole against the holder. Accordingly, with the optical head according to the present invention, a torque of rotation generated when the screw is rotated is absorbed in the bot-tom portion of the tapped hole, so that the holder is not moved when the screw is screwed into the tapped hole, where-by the optical element fixedly disposed on the holder can be easily positioned at an appointed position.

Description

13149(~5 BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to an optical head of an optical recording and reproducing device for optically carrying out the recording and the repro-duction of in~ormations or either of them.
Description of the Prior Art An optical head is disclosed, for example, in Japanese Utility Model Appln. Laid-Open No.
142829/1985. In that Utility Model, a housing member for housing a light source, an optical detector and the like are shown with the housing member being provided with a guide hole formed therein, and the guide hole being provided with a cylindrical holder, which is provided with at least one optical element fixedly disposed thereon, movably engaged therewith in the axial direction. A fixing screw is screwed in a tapped hole which is a through hole formed in the housing member whereby the holder is fixed to the housing member.
The holder is put in the guide hole. Then, the holder is moved in the axial direction to be posi-tioned so that the optical element, which is fixedly disposed on the holder, may be disposed at the appointed position determined in view of the optical design. Finally, the fixing screw is screwed into tha tapped hole to fix the holder.

~314'~ 5 Usually, accurac~ of micron order is required for the positioning of the optical element.
Howevex, since the pointed end of the fixing screw i5 in general unevenly shaped, with the above-described conventional optical head, when the fixing screw is screwed up, the position, at which the holder is first engaged with the fixing screw, does not come on the central axis of the fixing screw, whereby the holder is moved by the fixing screw until the appointed value of torque, at which the rotation of the fixing screw is stopped, is obtained. Accordingly, the conventional optical head has a problem in that it is difficult to dispose the optical element, which is fixedly disposed on the holder, at the appointed position.
SUMMARY OF THE INVENTION
The present invention was achieved for solving the above-described problem. In the optical head according to the present invention, a tapped hole is not a through hole reaching a guide hole but an opening with a bottom portion left and a fixing screw having a conical end is provided which is screwed into such a tapped hole and the end of the screw presses the bottom portion to deform the same causing the deformed portion to engage the holder and thereby fix the holder to the housing member.
Thus, it is a first object of the present invention to provide an optical head capable of easily . ~, ' fixedly disposing an optical element, which is fixedly disposed on a holder, at an appointed position.
It is a second object of the present invention to provide an optical head without requiring readjustment since the holder, which has finished the positional adjustment of the optical element, is not moved when fixed.
An optical head, in accordance with the present invention, i5 provided with a housing member for housing a holder, which holder is provided with an optical element which is fixedly disposed in a light path between a light source and an optical detector and is movable in the direction of an optical a~is in a guide hole formed therein. ~he optical head is provided for condensing a light from the light source onto a medium, condensing a re~lected light ~rom the medium onto the optical detector and detecting the reflected light by the optical detector. The optical head is characterized in that the housing member is provided with a tapped hole formed in a direction meeting substantially at right angles with the axial direction from a surface 50 as not to reach the guide hole -to leave a bottom portion having a thickness such that a screw screwed into the tapped hole fi~es the holder to the housing member by pressing a circum-ference of the holder.
The above and further objects and features of the invention will more fully be apparent from the 1 3 ~ 5 following detailed description with accompanyingdrawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view showing principal parts of the conventional optical head;
Fig. 2 is an enlarged sectional view showing principal parts o~ the conventional optical head;
Fig. 3 is a sectional view showing an optical head according to the present invention;
Fig. 4 is an enlarged perspective view showing principal parts of an optical head according to the present invention; and Fig. 5 is an enlarged sectional view showing principal parts of an optical head according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 and Fig 2 are a perspective view and a sectional view, respectively, showing the principal parts of the conventional optical head disclosed, for example, in Japanese Utility Model Appln. Laid-Open No.
14282g/1985. Referring now to Figs. 1 and 2, reference numeral 1 designates a housing member for housing a light source, an optical detector and the like (not shown) therein, the housing member 1 being provided wlth a guide hole 2 formed therein, and the guide hole 2 being provided with a cylindrical holder 3, which is provided with at least one optical element ~not shown) fixedly disposed thereon, movably engaged therewith in ;

1 3 1 1~ 9 i 1 ~1 the axial direction. And, a fixing screw 4 is screwed in a tapped hole 16 which is a through hole formed in the housing member 1, whereby the holder 3 is fixed to the housing member 1.
Next, the procedure for fixing the holder 3 to the housing member 1 is described.
At first, the holder 3 is put in said guide hole 2. Then, the holder 3 is moved in the axial direction to be positioned so that the optical element, which is fixedly disposed on the holder 3, may be disposed at the appointed position determined in view of the optical design. Finally, the fixing screw 4 is screwed into the tapped hole 16 to fix the holder 3.
Usually, accuracy of micron order is required for the positioning of the optical element.
However, since the pointed end of the fixing screw 4 is in general unevenly shaped, with the above-described conventional optical head, when the fixing screw 4 is screwed up, the position, at which the holder 3 is first engaged with the fixing screw 4, does not come on the central axis 4a of the fixing screw 4, whereby the holder 3 is moved by the fixing screw 4 until the appointed value of torque, at which the rotation of the fixing screw 4 is stopped, is obtained, as shown in Fig. 2. Accordingly, the conventional optical head has a problem in that it is difficult to dispose the optical element, which is fixedly disposed on the holder 3, at the appointed position.
- ~a -1 3 1 ~ 5 Fig. 3 is a sectional view showing an optical head according to the present invention, and Fig. 4 is a partial perspective view shawing the optical head shown in Fig. 3. Referring to Figs. 3 and 4, reference numeral 1 designates a housing member provided with a guide hole 2 formed therein~ reference numeral 8 designating an actuator, and reerence numeral 10 designating a medium. The housing member 1 is provided with a light source 7 disposed on an opened portion thereof, a prism 14 serving as a half mirror and a lens 13 for turning a light from the light source 7 into a parallel light bein~ disposed with optical axes thereo~ coincided with each other, and an objective lens 9 for condensing the parallel light from the lens 13 onto the medium 10 to form an image being housed in the actuator 8.
The housing member 1 is provided with an optical detector 11 for detecting a reflected light from the medium 10 on the opened portion of the side on which the guide hole 2 is - ~b -1 3 1 4 9 ~ ~

formed therein, and a cylindrlcal holder 3 provided with a lens 12 for condensing the reflec-ted light from the medium 10 onto the optical detector 11 fixedly disposed thereon be-ing put in the guide hole 2 so as to be movable in the a.~ial direction. The housing member 1 is provided with a tapped hole 6 formed on the circumference of -the guide hole 2 not so as to reach the guide hole 2, in short, so as to leave a bottom portion 5 having -the appointed -thickness and a fixing screw 4 is screwed into said tapped hole 6 to fix the holder 3 in the guide hole 2 of the housing member 1.
Next, the optical path in such an optical head is de-scribed.
~ light emi-tted from the light source 7 is passed through -the prism 14 to be turned into a parallel light by means of the lens 13 followed by focusing on the medium 10 in the form of a condensed spot by means of the objective lens 9 disposed within the actuator 8. The light focused on the medium 10 is reflec-ted and then turned into a parallel light by means of the objective lens 9 followed by bein~
condensed by means of -the lens 13 alld reflected by the prism 1~ to change a course thereof by 90 . The light reflected by the prism 1~ is collected onto the optical detector 11 by means of the lens 12.
In this time, it is necessary to adjust the position of the lens 12 so tha-t the ligh-t led to the optical detector 11 1 31 ~5 may be accurately focused on the optical detector 11. And, since the lens 12 is fixedly disposed on -the holder 3, the holder 3 is fixed to the housing member 1 and then -the posi-tion of the lens 12 is finally determined.
Next, the method of determining the posi-tion of the lens 12 and the method of fixing the holder 3 in the optical head according to the presen-t invention are described with reference to Fig. 5 in detail showing the fixed condition.
At first, the holder 3 is moved in the axial direction to adjust the position of the lens 12 so -that the light -to led to the optical detector 11 may be accurately focused on -the optical detector 11. After finishing the posi-tional ad-justment of the lens 12 the fixing screw 4 is screwed up along the tapped hole 6 provided in the housing member 1.
Thus, since the tapped hole 6 is formed with the bottom por-tion 5 left, the bottom portion 5 of the tapped hole 6 is deformed as the fixing screw 4 is screwed up to some extent and the deformed bottom portion 5 is pressed by the fixing screw 4, whereby the holder 3 is fixed to the housing member 1 (refer to Fig. 5).
As above described, according to the present invention, since the holder 3 is pressed by the fixing screw ~ throu~h the bottom portion 5 of the tapped hole 6 when the holder 3 is fixed to -the housing member 1, the torclue of rotation generated when -the fixing screw 4 is rotated is absor~ed in 131~9~5 the bottom por-tion 5 of -the -tapped hole 6, whereby only the fastening force is transmitted to the holder 3. Thus, the holder 3, of which posi-tional adjustment of -the lens 12 was finished, is not. moved when fixed, so -that the position of the optical element is not changed and the optical element can be easily disposed at the appointed position. Accord-ingly, it is unnecessary to readjust the position of tne holder 3.
In addition, although the lens 12 for condensing a light onto the optical de-tector 11 is fixedly disposed on the holder 3 in the above described preferred embodiment, the construction is not limited by this. The lens 13 for turning the light from the light source 7 into a parallel ligh-t may be fixedly disposed on the holder ~. .
In addition, in the cases where other optical elements, such as 1/2 wavelength plate, 1/4 wavelength plate and re-fractive lattice, are housed in the housing member 1, one or some of said other optical elements may be fixedly disposed on the holder 3.
As this invention may be embodied in several forms without departing from the spiri-t of essential characteris-tics thereof, the present embodiment is therefore il].ustra-tive and not restrictive, since the scope of -the invention is defined by the appended claims rather than by the de-scri.ption preceding them, and all changes that fall within 1 3 1 ~9~5 the meets and bounds of the claims, or equivalence of such meets and bounds thereof are therefore intencled to be em-braced by the claims.

Claims

1. An optical head provided with a housing member for housing a holder, which holder is provided with an optical element which is fixedly disposed in a light path between a light source and an optical detector and is movable in the direction of an optical axis in a guide hole formed therein, the optical head being for condensing a light from said light source onto a medium, condensing a reflected light from said medium onto said optical detector and detecting said reflected light by said optical detector, characterized in that said housing member is provided with a tapped hole formed in a direction meeting substantially at right angles with said axial direction from a surface so as not to reach said guide hole to leave a bottom portion having a thickness such that a screw screwed into said tapped hole fixes said holder to said housing member by pressing a circumference of said holder.

2. An optical head as set forth in claim 1, in which said optical element is a lens for condensing said reflected light from the medium onto the optical detector.

3. An optical head as set forth in claim 1, in which said optical element is a lens for condensing said light from the light source onto said medium.

4. An optical head as set forth in claim 1, in which said optical element is an optical element for changing said light path.

5. An optical head as set forth in claim 1, in which a circumference of said holder is pressed by a bottom portion of said tapped hole when the screw is screwed into the tapped hole.

6. An optical head as set forth in claim 1, in which said medium can record and reproduce information.

7. An optical head as set forth in claim 1, in which said medium can either record or reproduce information.